/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.Beta;
import com.google.common.annotations.GwtCompatible;
import com.google.errorprone.annotations.CanIgnoreReturnValue;

import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import javax.annotation.CheckForNull;

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A list which forwards all its method calls to another list. Subclasses should override one or
 * more methods to modify the behavior of the backing list as desired per the <a
 * href="http://en.wikipedia.org/wiki/Decorator_pattern">decorator pattern</a>.
 *
 * <p>This class does not implement {@link java.util.RandomAccess}. If the delegate supports random
 * access, the {@code ForwardingList} subclass should implement the {@code RandomAccess} interface.
 *
 * <p><b>Warning:</b> The methods of {@code ForwardingList} forward <b>indiscriminately</b> to the
 * methods of the delegate. For example, overriding {@link #add} alone <b>will not</b> change the
 * behavior of {@link #addAll}, which can lead to unexpected behavior. In this case, you should
 * override {@code addAll} as well, either providing your own implementation, or delegating to the
 * provided {@code standardAddAll} method.
 *
 * <p><b>{@code default} method warning:</b> This class does <i>not</i> forward calls to {@code
 * default} methods. Instead, it inherits their default implementations. When those implementations
 * invoke methods, they invoke methods on the {@code ForwardingList}.
 *
 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Mike Bostock
 * @author Louis Wasserman
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public abstract class ForwardingList<E extends @Nullable Object> extends ForwardingCollection<E>
        implements List<E>
{
    // TODO(lowasser): identify places where thread safety is actually lost

    /**
     * Constructor for use by subclasses.
     */
    protected ForwardingList()
    {
    }

    @Override
    protected abstract List<E> delegate();

    @Override
    public void add(int index, @ParametricNullness E element)
    {
        delegate().add(index, element);
    }

    @CanIgnoreReturnValue
    @Override
    public boolean addAll(int index, Collection<? extends E> elements)
    {
        return delegate().addAll(index, elements);
    }

    @Override
    @ParametricNullness
    public E get(int index)
    {
        return delegate().get(index);
    }

    @Override
    public int indexOf(@CheckForNull Object element)
    {
        return delegate().indexOf(element);
    }

    @Override
    public int lastIndexOf(@CheckForNull Object element)
    {
        return delegate().lastIndexOf(element);
    }

    @Override
    public ListIterator<E> listIterator()
    {
        return delegate().listIterator();
    }

    @Override
    public ListIterator<E> listIterator(int index)
    {
        return delegate().listIterator(index);
    }

    @CanIgnoreReturnValue
    @Override
    @ParametricNullness
    public E remove(int index)
    {
        return delegate().remove(index);
    }

    @CanIgnoreReturnValue
    @Override
    @ParametricNullness
    public E set(int index, @ParametricNullness E element)
    {
        return delegate().set(index, element);
    }

    @Override
    public List<E> subList(int fromIndex, int toIndex)
    {
        return delegate().subList(fromIndex, toIndex);
    }

    @Override
    public boolean equals(@CheckForNull Object object)
    {
        return object == this || delegate().equals(object);
    }

    @Override
    public int hashCode()
    {
        return delegate().hashCode();
    }

    /**
     * A sensible default implementation of {@link #add(Object)}, in terms of {@link #add(int,
     * Object)}. If you override {@link #add(int, Object)}, you may wish to override {@link
     * #add(Object)} to forward to this implementation.
     *
     * @since 7.0
     */
    protected boolean standardAdd(@ParametricNullness E element)
    {
        add(size(), element);
        return true;
    }

    /**
     * A sensible default implementation of {@link #addAll(int, Collection)}, in terms of the {@code
     * add} method of {@link #listIterator(int)}. If you override {@link #listIterator(int)}, you may
     * wish to override {@link #addAll(int, Collection)} to forward to this implementation.
     *
     * @since 7.0
     */
    protected boolean standardAddAll(int index, Iterable<? extends E> elements)
    {
        return Lists.addAllImpl(this, index, elements);
    }

    /**
     * A sensible default implementation of {@link #indexOf}, in terms of {@link #listIterator()}. If
     * you override {@link #listIterator()}, you may wish to override {@link #indexOf} to forward to
     * this implementation.
     *
     * @since 7.0
     */
    protected int standardIndexOf(@CheckForNull Object element)
    {
        return Lists.indexOfImpl(this, element);
    }

    /**
     * A sensible default implementation of {@link #lastIndexOf}, in terms of {@link
     * #listIterator(int)}. If you override {@link #listIterator(int)}, you may wish to override
     * {@link #lastIndexOf} to forward to this implementation.
     *
     * @since 7.0
     */
    protected int standardLastIndexOf(@CheckForNull Object element)
    {
        return Lists.lastIndexOfImpl(this, element);
    }

    /**
     * A sensible default implementation of {@link #iterator}, in terms of {@link #listIterator()}. If
     * you override {@link #listIterator()}, you may wish to override {@link #iterator} to forward to
     * this implementation.
     *
     * @since 7.0
     */
    protected Iterator<E> standardIterator()
    {
        return listIterator();
    }

    /**
     * A sensible default implementation of {@link #listIterator()}, in terms of {@link
     * #listIterator(int)}. If you override {@link #listIterator(int)}, you may wish to override
     * {@link #listIterator()} to forward to this implementation.
     *
     * @since 7.0
     */
    protected ListIterator<E> standardListIterator()
    {
        return listIterator(0);
    }

    /**
     * A sensible default implementation of {@link #listIterator(int)}, in terms of {@link #size},
     * {@link #get(int)}, {@link #set(int, Object)}, {@link #add(int, Object)}, and {@link
     * #remove(int)}. If you override any of these methods, you may wish to override {@link
     * #listIterator(int)} to forward to this implementation.
     *
     * @since 7.0
     */
    @Beta
    protected ListIterator<E> standardListIterator(int start)
    {
        return Lists.listIteratorImpl(this, start);
    }

    /**
     * A sensible default implementation of {@link #subList(int, int)}. If you override any other
     * methods, you may wish to override {@link #subList(int, int)} to forward to this implementation.
     *
     * @since 7.0
     */
    @Beta
    protected List<E> standardSubList(int fromIndex, int toIndex)
    {
        return Lists.subListImpl(this, fromIndex, toIndex);
    }

    /**
     * A sensible definition of {@link #equals(Object)} in terms of {@link #size} and {@link
     * #iterator}. If you override either of those methods, you may wish to override {@link
     * #equals(Object)} to forward to this implementation.
     *
     * @since 7.0
     */
    @Beta
    protected boolean standardEquals(@CheckForNull Object object)
    {
        return Lists.equalsImpl(this, object);
    }

    /**
     * A sensible definition of {@link #hashCode} in terms of {@link #iterator}. If you override
     * {@link #iterator}, you may wish to override {@link #hashCode} to forward to this
     * implementation.
     *
     * @since 7.0
     */
    @Beta
    protected int standardHashCode()
    {
        return Lists.hashCodeImpl(this);
    }
}
